The OSD uuid is being required as an extra step to ensure that the
right OSD is being activated. It is entirely possible that a previous OSD with
the same id exists and would end up activating the incorrect one.

Would start the discovery process for the OSD with an id of 0 and a UUID of
8715BEB4-15C5-49DE-BA6F-401086EC7B41.

The systemd process will call out to activate passing the information needed to
identify the OSD and its devices, and it will proceed to:

# mount the device in the corresponding location (by convention this is

/var/lib/ceph/osd/<clustername>-<osdid>/)

# ensure that all required devices are ready for that OSD and properly linked,
regardless of objectstore used (filestore or bluestore). The symbolic link will
always be re-done to ensure that the correct device is linked.